You can trap anywhere. Do it out of the public eye, hide your trapsets and attract the squirrels to where you want to trap. You can use birdseed to attract the birds, the squirrels will see the commotion and be over post haste.

Set up disabled traps where you're chumming the birds, then when the squirrels show up, cease feeding the birds, re-enable the traps and get ready for action. You can also let them get the bait a few times, get them confidant and careless.